Power transmission chains comprising a plurality of sets of transversely aligned links which are interleaved with other sets of links are well known. Each link has a pair of spaced apertures, and the individual links are arranged into transversely aligned sets of links. One array of apertures of a first set of links is transversely aligned with an aperture array of the set of interleaved links, to thus define a group of aligned apertures. A pivot means is inserted in each group of transversely aligned apertures to join the interleaved sets of links and permit articulation of the assembly of links. The pivot means for joining the links can be single round pins, or what is known as rocker joints. Rocker joints comprise a pair of pins or a pin and a rocker, each having a surface in rocking engagement with the other. The links can be of the "silent" chain type having a pair of toes, or they can be similar to the roller chain type.
Chains of the type described are also used in the manufacture of chain-belts, i.e., a chain and load block combination, especially suitable to provide a driving connection between a pair of pulleys. Pulley transmissions providing a variable ratio drive are being tested for use in fuel efficient automobiles. Variable ratio pulley transmissions are also known as continuously variable transmissions or CVTs. In variable pulley transmissions, each pulley is constructed of a pair of flanges or sheaves, at least one of which is axially movable with respect to the other. A drive belt suitable for use in variable pulley transmissions is taught by U.S. Pat. No. 3,720,113. The belt is constructed of a plurality of superimposed and matched metal bands, and abutting drive or load blocks surround the bands. A belt so constructed is relatively expensive to manufacture because of the close tolerances required in the matching of the bands, and mounting of the load blocks so that each abuts the adjacent blocks.
Rocker joints are well known in the art. Some examples are illlustrated in U.S. Pat. Nos. 3,540,302, 3,742,776 and 4,010,656. U.S. Pat. No. 3,540,302 shows a roller chain having a rocker joint comprising a pair of like members, and each member has a surface in rocking engagement with a like surface of the other member. The rocking surface of each is defined by a first radius, while the remainder of the member is defined by a surface of a second, and smaller, radius. Both surfaces of each member are convex. The apertures for receiving the joint members are generally rectangular, and each joint member has spaced notches in which the link members seat to transmit the working load to the assembly.
U.S. Pat. No. 3,742,776 discloses a silent chain with a rocker joint comprising a pair of like members, each having a rocking surface engaging the other. The rocking surfaces are defined by a first radius, while the back surfaces of each member are defined by a second, and smaller, radius. The rocking and back surfaces are joined by planar or straight surfaces. The links of the chain have apertures formed of inner and outer circular segments joined by wall segments which define straight chords of the circle. The members of the rocker joint are wedged into the apertures of a set of links, leaving a space between the back surface of the joint members and the walls of those apertures.
U.S. Pat. No. 4,010,656, which is owned by the assignee of the present invention, relates to a chain constructed of sets of interleaved links, each link having a pair of spaced, smooth walled, ovoid apertures. The rocker joint comprises a pair of members of like hypotrochoidal cross-sectional configuration. Each joint member has three convex surfaces of geneally equal size and of a first radius, joined by corner surfaces of a second and lesser radius. The elements substantially match the shape of parts of the apertures of a set of links, and engage those aperture parts with a pair of the convex surfaces and a joining corner surface.
In some forms of power transmission chains, one of the pivot members of a rocker joint is longer than the other. The shorter member is retained in position by guide links flanking the edges of the chain, and the longer of the pivot members is press-fit or otherwise secured in the guide links. In another form of chain, the pivot members or one of the members is press-fit into normal edge links.
The tensile strength of a chain with pivot elements press-fit into links is limited by the tensile strength of those links. Because of the press-fit of the pivot elements, the tensile strength of those links is usually less than the tensile strength of the other links in the chain. It has been suggested in an application for U.S. letters patent, Ser. No. 442,387, filed concurrently herewith, to use clip-like retaining members to position the pivot members, i.e., rocker joint members or round pins, in the links, so that the joint members need not be press-fit in some of the links. The use of the clip-like retaining members provides a chain having an improved tensile strength.